The nearly 7-foot grand piano looked out the living room picture window at Lake Riley. Prince would often sit here and play late into the night. Or sometimes he’d walk by and just noodle a gospel riff on the keys.

At this keyboard one night in 1983 in his soon-to-be-purple house in Chanhassen, Prince recorded a work tape that has become the first posthumous project from his famous Paisley Park vault stuffed with thousands of unreleased and unfinished recordings. And a revelatory record it is for his followers.

A once-prized bootlegged tape, “Piano & a Microphone 1983” is being officially released Friday as a bookend — musically and titularly — to the Minnesota icon’s final public appearances in 2016 on his solo Piano & a Microphone Tour.

The final concerts offered a freewheeling, 90-minute or so journey through his catalog and influences as he sat at a purple grand piano. The new album is a stream-of-consciousness half-hour or so piano exploration through ideas and influences, including a verse-and-chorus snippet of an embryonic “Purple Rain,” an equally brief reading of Joni Mitchell’s “A Case of You” and full versions of Prince’s “17 Days” and the spiritual “Mary Don’t You Weep.”

All were performed on piano at a time when music lovers thought that guitar was Prince’s main instrument. And, of course, he recorded this work session at the black Yamaha keyboard — just like he taped every rehearsal, jam, concert, nearly every musical moment.

“It was a pretty normal exercise for him to feel out the songs, but this ended up being extraordinary because of the time of his life and what would happen after this,” said Lisa Coleman, the Prince & the Revolution keyboardist who lived in the house on Kiowa Trail with Prince in 1982-83.

She had the pink bedroom on the main floor, his bedroom was in the basement — “his groovy man cave with a furry rug and fluffy bedspread” — down the hall from his recording studio and laundry room. The living room in this modest 1960s split level ranch-style house had mirrored walls to make it seem bigger.

What’s fascinating about this 1983 recording is you can almost hear Prince thinking as he sat at the piano, composing, problem-solving and working his way through arrangements. It’s an artist creating in real time. There is humming, scatting, grunting, finger snapping and wordless vocalizing as well as actual lyrics in some cases.

No editing of cassette

When sorting through the contents of the Purple One’s vault last year, Michael Howe, chief archivist for the Prince estate, found this treasure in a box of cassettes. The only identification was two song titles — “Cold Coffee and Cocaine” and “Why the Butterflies” — in Prince’s handwriting on the B-side of a TDK C60 cassette.

“It’s exactly as it happened,” Howe said of the recording. “There’s no editing, no cross-fading, no manipulation of any kind.”

The piano was wired into the recording studio in the basement and you can hear Prince asking someone to flip the tape. To hear the shy and mysterious burgeoning rock star — who at this time already had the hits “Little Red Corvette” and “1999” — say something mundane was rare, at least until the movie “Purple Rain” came out in July 1984. He had a deep speaking voice in contrast to his falsetto-loving singing style.

In the vault, Howe found handwritten lyrics to “17 Days,” in a batch of other papers. These kinds of materials were often left in boxes containing reel-to-reel studio recordings.

The archivist turned to three people to contribute liner notes — Coleman, engineer Don Batts and Jill Jones, a singer and Prince insider who appeared in the film “Purple Rain” and later recorded for Paisley Park Records.

“Prince played the piano like he was playing WITH it. A cat toying with a mouse,” Coleman wrote. “When he played funk, gospel, or rhythm stuff, his body started moving before his hands hit the keys! He would stomp his foot and grunt in the spaces. He could hear the whole conversation, and his groove was unbeatable. In so many ways, Prince existed in the in-between of things. His breath was as important as his voice.”

In an interview, Coleman said Prince played the piano all the time, often late at night. It was never loud enough to keep her awake but she recalls one time when he was asleep and she was playing. “The next day,” she remembered, “he said it was nice to hear the music while he was sleeping.”

An on- and off-again girlfriend of the rock star, Jones would oftentimes sit under the piano, lying on the always-vacuumed black shag carpet, listening to the barefoot Prince play.

“He’d go on for hours,” Jones recalled in an interview this week. “It was just really serene and peaceful, and you could see the lake. It was really, really pretty.”

Meet Jamie Starr

One of the previously unreleased songs on the new album, “Cold Coffee and Cocaine,” is the first official recorded evidence of Prince’s alter ego, Jamie Starr, the name he famously used when producing and writing for the Time, Vanity 6 and others.

“It was a go-to character we witnessed every day,” Coleman said of the shady, sexy, playful and sometimes crude Starr. “That was Prince. He was like the weather: He was four seasons in one day.”

The jazzy “Cold Coffee and Cocaine” is filled with grunts and groans like James Brown dancing on the keyboard before Prince sings in a raspy voice that suggests Miles Davis having a conversation with 88 keys.

Another unreleased song, “Why the Butterflies,” opens with a gentle chord, moves into spacey piano before Prince starts vamping and asking his mother questions. At one point, in a lonely weeping wail, he demands, “Mama, where is father?”

“Wednesday,” sung in a falsetto voice, is a piece Prince penned for Jones’ waitress-at-First-Avenue character in the upcoming movie “Purple Rain.” “When he wrote she was contemplating suicide, people thought that was a little bit severe for this character,” Jones said of her song. “So he changed the line to ‘contemplating your embrace.’ ”

The scene featuring Jones singing “Wednesday” got cut from the movie, but Prince’s version on the new album has the original suicide lyric.

His gospel side

There are nine numbers on “Piano & Microphone 1983,” though the first seven run together like a long medley. We hear only a sip of “A Case of You” but some selections are complete, like “17 Days,” which would become a B-side to 1984’s smash “When Doves Cry”; “Strange Relationship,” which would show up on 1987’s “Sign o’ the Times” album, and “International Lover,” which was on 1982’s “1999” album.

In “Mary Don’t You Weep,” the Purple One doesn’t mention Moses or Pharaoh’s army that are heard in the usual versions of this spiritual; rather he improvises lyrics about disliking winter and Mary cooking the greatest omelets in the world.

Prince’s rendition, with all its cool gospel piano runs, is featured during the closing credits of director Spike Lee’s current movie, “BlacKkKlansman.” A new music video for the song focuses on a theme of gun violence and youth — Prince does not appear in the video.

“I don’t think people really knew that gospel side of him,” Coleman said. “He was rebelling against that. ‘I’m a rude-boy, punk-funk guy. I’m not going to go to church.’ But that’s his soul, and that style came out of him so fluidly.”

“Piano & a Microphone 1983” is the first in a series of posthumous new releases from the vault. The estate also has entered into a deal with Sony Music to reissue some of Prince’s studio albums, beginning in 2021.

Howe said the six heirs have been “involved in every step” of this process and that he has “educated them about the vault.” The decisions about what will be released are up to the estate administrator, Comerica, and its entertainment adviser Troy Carter.

No word yet on what’s next from the vault but Howe thinks it has enough quality material — audio and video — to keep new releases coming for many, many years.